Gaps? Cupping? Relative Humidity Is Important to Wood

The National Wood Flooring Association recommendations regarding solid wood flooring: HVAC must be in operation before, during and after installation. A temperature of 70 degrees F ±10 degrees and a relative humidity between 35–55 percent is recommended. Heating units or uninsulated ductwork close to the flooring or subfloor may cause hot spots, which must be eliminated prior to installation. Moisture testing is critical. Confirm proper drainage exists around the structure. In crawl spaces exposed earth must be fully covered with minimum six mil polyethylene sheeting. In unconditioned crawl spaces (crawl spaces without heat and humidity control,)﻿vents must be open at all times and must equal at least 1.5 percent of the total square footage of the crawl space. Basements must be dry and remain dry.﻿

A floor in a house that is too dry will develop gaps between the boards. Our windows were not built for "Polar Vortex" winters. Even with a good humidifier on your furnace, cold windows may cause the moisture in the air to condense. Cover your windows when the sun is not shining. Keep moisture in the air, not on the windows.﻿

Wet mopping can make floor boards cup. Wood floors should be damp mopped.﻿ Floor boards that have taken on too much moisture will cup.

A relative humidity of 30 - 55 % is recommended. For greatest accuracy, get a digital hygrometer, or calibrate your analog hygrometer.

If your floor has permanent gaps, they can be filled with wood filler during the refinishing process, although the filler will most likely fall ﻿out, due to movement or seasonal changes in the floor.

A light stain can help to conceal gaps by adding contrast withing each board, rather than emphasizing the contrast (and the gaps) between boards. ﻿

Color Putty is an oily filler that is used after finish is applied to fill gaps. Choose a color that will blend with your floor. Push it into the gap or knot and wipe off excess. It is not as brittle as trowelled on or wood flour filler and may stay in a gap longer.

Large gaps can have slivers (also called Dutchmen,) thin strips of wood, glued into the cracks during the refinishing process.

If your floor is sanded and finished when the humidity is too high and the boards are cupped, you may have the opposite, crowning, when the relative humidity in your home drops.

For the flattest floor, maintain a relative humidity of 30 - 55%.

Cupping is when the edges of the board lengths are high.

Crowning is when the centers of the board lengths are high.

Gaps are spaces that appear between rows of boards.

What can we do for you? Call us for a free home estimate. 248-627-5643